Polishing system

ABSTRACT

A polishing method characterized by measuring the thickness of a film of a monitoring piece to be polished which is to be used exclusively for monitoring polishing amount, and obtaining polishing amount on the basis of the results of measurement, and judging, on the basis of the resulting polishing amount, setting/change of polishing condition of a polishing object, whether it is necessary or not to replace a polishing pad, and/or completion of run-in polishing after replacement of the polishing pad, and an apparatus to be used for practicing same.

BACKGROUND OF THE INVENTION

The present invention relates to a polishing system for polishingobjects such as wafers, glass substrates, and the like which have filmson their surfaces.

For example, in the manufacturing process of Large Scale Integration(LSI), wiring patterns for forming transistors, capacitors, and the likeare formed on a silicon wafer substrate or the like, and further aninsulating film is formed over the whole surface. At such time, theunderlying wiring pattern causes parts of the surface of the insulatingfilm to be uneven. In the recent LSI manufacturing technique, in orderto make the wiring pattern multi-layered, the insulating film having theuneven surface is required to be flattened. In order to flattenier levelthe insulating film having the uneven parts, a Chemical MechanicalPolishing (CMP) method is generally utilized.

In case of carrying out successively polishing of the films such as aninsulating film having the uneven parts formed on the wafer by CMPmethod, there is used in general a method of previously measuringpolishing speed, estimating the polishing time based on the polishingspeed, and effecting polishing at the estimated polishing time.According to this method, in case the polishing speed and uniformity inthe wafer surface thereof are stabilized with time, the wafer can bepolished in stabilized state for a long duration.

However, the polishing speed varies depending on the change with time ofthe surface condition of a polishing pad, irregularity of quality of thepolishing slurry, and the like Accordingly, in case of a necessity tocontrol polishing amount in high precision, the change with time of thepolishing speed is required to be considered.

As a method for considering the change with time of the polishing speed,in case of polishing the wafer provided with a film having the unevenparts successively, there is proposed a method of obtaining thickness ofthe film before and after the polishing with an optical film thicknessgauge, obtaining polishing speed, and then reset polishing time(Japanese Patent Application Laid-Open No. 8-17768 (1996).

According to this method, the polishing time can be varied in accordancewith the change with time of the polishing speed, and therefore thepolishing amount can be kept a constant value.

According to this method, however, the wafer to be the product such asLSI (hereinafter to be referred to as "product wafer"), i.e., waferprovided with a film having convex and concave regions, is used formeasuring the polishing speed, so that it involves the followingproblems.

(1) Because of the fine patterns formed on the product wafer, even onslight displacement of the measuring position, change occurs in the filmbase, such as for example from silicon to aluminum. For this reason, ifthere is any displacement in the measurement position, then the measuredamount of the film thickness becomes inaccurate.

(2) Depending on convex or concave part, if there is a slightdisplacement in the measurement position, the film thickness varies to aconsiderable degree. Therefore, it is difficult to measure the filmthickness accurately.

(3) In recent years, there are frequently cases where, with the objectof preventing reflection, an intermediate film of TiN or the like isused for the base of the film. In such a case, due to the presence ofthe intermediate film, precision of film thickness measurement isdegraded.

As described above, in case a product wafer is used for measuring thepolishing speed, there is a problem to make the film thicknessmeasurement value inaccurate. When the film thickness measurement valueis inaccurate, evaluation of the polishing amount (polishing speed)becomes inaccurate, and proper determination of the polishing timecannot be made, so that the desired amount of polishing can not beobtained.

In order to obviate such problem of measurement, there may be conceivedto measure the film thickness of only the peripheral part of the waferon which no LSI device is formed, i.e., without having convex or concavepart. However, by only he measurement of the film thickness of theperipheral part of the wafer, it is not possible to evaluate thepolishing situation at the central part of the wafer on which the LSIdevice is practically to be formed. Furthermore, it is also difficult toevaluate the uniformity inside the wafer surface which is an importantindex.

Furthermore, in case of replacement of the polishing pad in the CMPdevice, the polishing process for the product wafer is started after thefollowing trial operation.

First, in order to stabilize the wafer polishing situation, break-inpolishing is carried out. This is a processing to place a dummy waferfor break-in polishing such as silicon wafer (hereinafter to be referredto as "dummy wafer") on a sample stage and continue polishing to makethe polishing slurry sufficiently be absorbed by the polishing pad.

The time of completion of the break-in polishing (i.e., the startingpoint of polishing the product wafer) is determined by experience by theworker. However, the worker's judgment by experience is apt to causeerrors.

BRIEF SUMMARY OF THE INVENTION

The present invention has been devised to solve the above problems. Itis therefore an object of the present invention to provide a polishingsystem in which, in polishing an object to be polished, it is possibleto meet the change with time of the polishing situation such aspolishing speed attributed to the degradation of the polishing pad orthe like, and to expect stabilization of the polishing amount anduniformity in the surface thereof.

The polishing system according to the present invention is characterizedby measuring the change in thickness of the film in an object to bepolished which is to be used exclusively for monitoring the polishingamount (hereinafter to be referred to as "monitoring piece"), andobtaining the polishing amount based on the results of measurement.

As the polishing amount is to be measured by using the monitoring pieceindependent from the polishing object, even if the object to be polishedhas uneven parts on the surface, the polishing amount can be accuratelydetermined without respect to such irregularities.

The object to be polished is, for example, a wafer for the product onthe surface of which an LSI device is to be formed, on the surface ofwhich a film having convex and concave regions is formed. On the otherhand, the monitoring piece is an object to be polished, to be used forevaluating the polishing situation, and is a sample having formed on thesurface a film such as a thermal oxidation film, or a plasma oxidationfilm (e.g., SiO₄ -O₂ type plasma oxidation film (P-Sio film), and TEOS(Tetra Ethyl Ortho Silicate: Si(OC₃ H₅)₄)-O₂ type plasma oxidation film(P-TEOS film)) or the like. Further, preferably, the film of themonitoring piece is flat without pattern formation, and its filmthickness is uniform.

The invention is further characterized by judging, on the basis of thechange in thickness of the monitoring piece film resulting frompolishing (=polishing amount), setting/change of the polishingconditions of the product wafer, requirement to change or not to changeof the polishing pad, and/or completion of the run-in polishing afterreplacement of the polishing pad (i.e., adequacy or not of the start ofpolishing of the predetermined object of polishing).

For example, it is possible to obtain a polishing speed from thepolishing amount. Moreover, by setting a plurality of measuring pointson one polishing object, various indices such as uniformity in surfaceof the polishing amount, polishing shape tendency value, and the likecan be obtained. Furthermore, in an apparatus with which a plurality ofobjects to be polished can be processed in a single polishing process (1batch), it is possible to obtain uniformity in a batch by providing ameasuring point on each of all polishing objects placed on therespective positions.

Accordingly, in the present invention, proper setting and change of thepolishing conditions can be automatically practiced on the basis of theindex value by obtaining the index necessary for setting/change of forexample the polishing conditions (e.g., polishing speed, uniformity inplane of the polishing speed, and the like) from the polishing amount.

Also, it is possible to judge automatically by the apparatus thenecessity or not of replacement of the polishing pad by obtaining anindex necessary for judgment of the requirement or not of the polishingpad (e.g., polishing speed, uniformity in plane of the polishing speed,and the like) from the resulting polishing amount.

Furthermore, in the run-in polishing after replacement of the polishingpad, by obtaining the polishing amount, completion of the run-inpolishing can be judged by the apparatus and polishing of the wafer forproduct can be automatically started.

According to these constitutions, due to the curtailment of the portionsparticipated by the person, the work can be performed efficiently, andbecause of the judgment not being dependent on the personal experience,scattering of judgments is small. Consequently, polishing amount of theobject to be polished such as wafers for product, uniformity in theplane of the polishing amount, and the like can be stabilized.

These constitutions can be adequately combined to obtain the individualeffects.

The polishing system according to the present invention is equipped witha CMP device, a washing device, a film thickness measuring gauge, acontainer for storing the monitoring pieces as mentioned above, acarrier for circulating in order of the container, polishing device,washing device, measuring device, and the container, and a calculatingunit. And, by making the thickness of the film of the monitoring piecesufficiently thick, the monitoring piece can be used in repetition. As aresult, frequency of carrying in and out of the monitoring piece can bereduced, and operation rate of the apparatus can be improved.

The above and further objects and features of the invention will morefully be apparent from the following detailed description withaccompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a block diagram showing a constitution of a CMP deviceaccording to Embodiment 1;

FIG. 2 is a flow chart showing a processing procedure of a polishingmethod in Embodiment 1;

FIG. 3 is a flow chart showing the judgment step of an index ofpolishing situation of FIG. 2;

FIG. 4 is a schematic plan view showing measuring points on a wafer anda wafer table;

FIG. 5 is an explanatory view for illustrating a method of judgingpolishing pad replacement, and a method of judging change of polishingconditions;

FIG. 6 is a block diagram showing a constitution of a CMP deviceaccording to Embodiment 2;

FIG. 7 is a flow chart showing a processing procedure for polishingmethod in Embodiment 2;

FIG. 8 is a block diagram showing a constitution of a CMP deviceaccording to Embodiment 3;

FIG. 9 is a schematic plan view of the CMP device body shown in FIG. 8;

FIG. 10 is a schematic side view of the film thickness measuring partshown in FIG. 9;

FIG. 11 is a schematic plan view showing a wafer flow in a monitor wafercontaining processing mode;

FIG. 12 is a schematic plan view showing a wafer flow in a product waferpolishing processing mode;

FIG. 13 is a schematic plan view showing a wafer flow in a monitor waferpolishing processing mode;

FIG. 14 is a schematic plan view showing a wafer flow in a monitor waferrecovery processing mode; and

FIG. 15 is a schematic plan view showing a wafer flow in a dummy waferpolishing processing mode.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in detail with referenceto the drawings which show the embodiments thereof. For example, a waferfor manufacturing LSI is called a product wafer, a wafer for monitoringpolishing amount is called a monitor wafer, and a wafer for run-inpolishing is called a dummy wafer.

Embodiment 1

FIG. 1 is a block diagram showing a polishing system according toEmbodiment 1. This polishing system comprises a CMP device body 1 and acontrol calculator 8 for controlling the same.

The CMP device body 1 comprises a wafer supply unit 2, a monitor wafercontaining unit 4, a film thickness measuring unit 5, a CMP unit 6, awashing unit 7, and a wafer carrier unit 11.

According to the processing mode set and indicated from the controlcalculator 8, each unit of the CMP device body 1 is constituted tooperate in cooperation. Processing mode includes, for example, a productwafer polishing processing mode, monitor wafer containing processingmode, monitor wafer polishing processing mode, and monitor waferrecovery processing mode.

The product wafer polishing processing mode is a mode to make polishingprocessing of the product wafer. The product wafer is carried to the CMPunit 6 and the washing unit 7 from a product wafer cassette stored inthe wafer supply unit 2, subjected to CMP and washing processes, andreturned to the product wafer cassette in the wafer supply unit 2.

The monitor wafer containing processing mode is a mode to store themonitor wafer in the monitor wafer containing unit 4. The monitor waferis transmitted to the film thickness measuring unit 5 from a monitorwafer cassette housed in the wafer supply unit 2, and after measurementof the film thickness, stored in the monitor wafer containing unit 4.

The monitor wafer polishing processing mode is a mode to polish themonitor wafer and to measure the polishing amount. The monitor wafer iscarried to the CMP unit 6 and washing unit 7 from the monitor wafercontaining unit 4, subjected to polishing and washing processes, carriedto the film thickness measuring unit 5, and after measurement of thefilm thickness, returned to the monitor wafer containing unit 4.

The monitor wafer recovery processing mode is a mode for carrying themonitor wafer outside the apparatus from the monitor wafer containingunit 4. The monitor wafer is transmitted to an empty monitor wafercassette contained in the wafer supply part 2 from the monitor wafercontaining unit 4 and withdrawn there.

The control calculator 8 comprises a polishing situation indexcalculating unit 42, a polishing situation judging unit 43, a temporarystoppage instructing unit 44, a pad replacement judging unit 45, a padreplacement instructing unit 46, a polishing condition setting unit 47,an apparatus control unit 48, and a mode selection unit 49.

The polishing situation index calculating unit 42 comprises a filmthickness memory unit and a calculation unit. The film thickness memoryunit stores the thickness of the film obtained in the film thicknessmeasuring unit 5, and the calculation unit calculates the polishingamount (that is, the amount or thickness of the layer removed inpolishing the monitoring piece) and other indexes showing the polishingsituation (hereinafter to be referred to individually or collectively asthe polishing situation index) from the film thickness prior topolishing stored in the film thickness memory unit and the filmthickness after polishing.

The polishing situation judging unit 43 judges as to whether thepolishing situation index obtained in the polishing situation indexcalculating unit 42 is within the allowable range or not. Namely, itjudges whether there is any deficiency unit in the polishing situationor not, and whether the polishing is properly carried out or not. Thetemporary stoppage instructing unit 44 instructs temporary stoppage ofthe CMP device body 1 when the polishing situation index is not withinthe allowance range.

The pad replacement judging unit 45 judges whether the polishing pad isto be replaced or not on the basis of the polishing situation index. Thepad replacement instructing unit 46 instructs to replace the polishingpad when judgment is made to replace the polishing pad.

The polishing condition setting unit 47 sets the polishing conditionsfor the product wafer. Firstly, judgment is made as to whether thechange of the polishing conditions is necessary or not, from thepolishing situation index. The polishing condition is changed whenjudgment is made that the change of the polishing conditions isnecessary.

The mode selection unit 49 selects any of the product wafer polishingprocessing mode, monitor wafer containing processing mode, monitor waferpolishing processing mode, and monitor wafer recovery processing mode asdescribed above. The apparatus control unit 48 indicates the operationto the CMP device body 1 on the basis of the indication from the modeselection unit 49.

The polishing situation index is explained. As the polishing situationindex, there may be used, for example, polishing amount, uniformity ofpolishing amount in wafer plane, uniformity of polishing amount inbatch, inclination amount of polishing shape, average polishing speed,and the like. In the present specification, "1 batch" is referred to byone time polishing with the apparatus which polishes a plurality ofwafers at the same time.

FIG. 4 is a schematic plan view showing measuring points on the waferand a wafer table. On the wafer table 21, there are placed five wafers,and 5 wafers can be polished in one batch. Also, on the wafer there areset 17 film thickness measuring points aligned in a cross line form.

The polishing amount X_(ij) (i=1-5, j=1-17) is obtained by subtractingthe film thickness after the polishing from the film thickness beforepolishing. Here, the mark i is a number of the 5 wafers of one batch,and j shows a measuring point on one wafer.

The average polishing amount by wafer x_(i), average polishing amount inone batch x, uniformity of polishing amount in plane by wafer σ_(i),uniformity in batch S, inclination amount of polishing shape K_(i), andaverage polishing speed R_(p), may be computed by Equations (1)-(10), onpages 39 and 40 wherein max is the maximum value in parentheses, min isthe minimum value in parentheses. The mark t_(mon) is a polishing timefor the monitor wafer. The polishing shape inclination amount K_(i) is,as seen from its definition equation (9), representative of aninclination of the difference of polishing amounts between the centralpart of wafer and the peripheral part of wafer.

Equations (1)-(10)

Next, a polishing method according to the present invention isexplained.

FIG. 2 is a flow chart showing the processing procedure of the polishingmethod according to the present invention.

(1) Previously, the thickness of the film of the monitor wafer ismeasured by the film thickness measuring unit 5 (Step S1). The filmthickness is stored in the polishing situation index calculating unit 42in the control calculator 8 as a film thickness prior to polishing ofthe monitor wafer.

This measurement is carried out in the monitor wafer containingprocessing mode as described above. Also, by carrying out this modesimultaneously with the trial operation after replacement of thepolishing pad, reduction of time loss can be done. In case of thecompletion of the monitor wafer containing processing at the time of thetrial operation after replacement of the polishing pad, the step SI maybe omitted.

(2) The polishing conditions for the product wafer are to be setinitially at the polishing condition setting unit 47 (Step S2). Thepolishing conditions include polishing time, rotation speed of wafertable 21, rotation speed of polishing pad, load of polishing pad, kindand flow volume of polishing slurry, temperature of washing liquid,washing speed, and the like, which may be determined by the result ofthe trial operation after replacement of the polishing pad.

(3) The polishing conditions for the product wafer are stored in theapparatus control unit 48 (Step S3).

(4) On the basis of the stored polishing conditions, the CMP unit 6polishes the product wafer, and the washing unit 7 washes it (Step S4,product wafer polishing processing mode).

(5) Whether to monitor the polishing situations or not is judged by theapparatus control unit 48 (Step S5). This judgment may be made by thenumber of processing of the product wafer and the like. For example, itis determined to monitor every 50 wafers (2 cassettes).

In case of it is judged not to monitor (a predetermined number of wafersare not done), the process returns to the processing step S4 of productwafer.

(6) In case of it is judged to monitor (the predetermined number isattained), the monitor wafer is polished on the basis of thepredetermined polishing conditions and washed (Step S6, monitor waferpolishing processing mode). The polishing conditions of the monitorwafer may be the same as those of the product wafer, and the polishingtime may be shortened.

(7) The thickness of the film of the polished and washed monitor waferis measured at the film thickness measuring unit 5 (Step S7, monitorwafer polishing processing mode).

(8) From the results of measurement of the film thickness, the polishingsituation index calculating unit 42 computes the polishing situationindices such as the polishing amount, in plane uniformity of polishingamount on one wafer, uniformity in batch of polishing amount, polishingshape inclination amount, average polishing speed, and the like (StepS8).

(9) The polishing situation judging unit 43 judges whether the resultingpolishing situation index is within the allowable range or not (StepS9).

FIG. 3 is a flow chart showing concretely Step S9. First, judgment ismade as to whether the uniformity in plane σ_(i) of the polishing amountis within the permissible range (σ_(i) <4%) or not (Step S22), and if itis within the range, judgment is made as to whether the uniformity inbatch S of the polishing amount is within the allowable range (-2%<S<2%)or not (Step S23), and if it is within the range, judgment is made as towhether the polishing shape inclination value K_(i) is within theallowable range (-5%<K_(i) <5%) or not (Step S24). In case it is judgedto be outside the allowable range in Steps S22, S23, and S24, thetemporary stoppage instructing unit 44 displays an error, stopstemporarily the processing of the CMP device body 1 (Step S25), andterminates the processing of the control calculator 8.

In case the polishing situation index is outside the permissible range,there is a possibility for abnormality such as defective fixing ofpolishing pad, defective supply of slurry, or the like in the CMPdevice. In such a case, it is necessary to discontinue automaticoperation with the control calculator 8 and make confirmation by theworker.

(10) In case that all the predetermined polishing situation indices arewithin the allowable range, the pad replacement judging unit 45 judgeswhether the polishing pad replacement is necessary or not, on the basisof, for example, whether the average polishing speed R_(p) is within thepredetermined range or not (Step S10). In case the replacement is judgedto be necessary, by the instruction of the pad replacement instructionunit 46, the polishing processing is temporarily stopped and replacementof pad and trial operation are indicated (Step Sll). Thereafter, theprocedure is returned to step S1, pre-polishing film thicknessmeasurement of monitor wafer is made, and processing is restarted.

(11) In case that the replacement of pad is judged to be unnecessary, onthe basis of the status for example as to whether the average polishingspeed R_(p) is within the predetermined range or not, judgment is madeas to whether the change of the polishing conditions of the productwafer is necessary or not, by the polishing condition setting unit 47(Step S12).

There is explained with reference to FIG. 5 a method of using theaverage polishing speed R_(p) in the judging step S10 for replacement ofpolishing pad and the judging step S12 for polishing condition change.To the target value R_(aim) of the preset average polishing speed R_(p),the ranges of the levels 1, 2, and 3 are set. In the examples shown inFIG. 5, values which are C<A<R_(aim) <B<D are set, the level 1 isA≦R_(p) ≦B, level 2 is C≦R_(p) ≦A, B≦R_(p) ≦D, and level 3 is R_(p) <C,D<R_(p). And, judgment is made in the following manner.

In case the average polishing speed R_(p) is in the range of level 3,replacement of the polishing pad is indicated. In case the averagepolishing speed R_(p) is in the range of level 2, the polishing pad isnot replaced, but the polishing conditions of the product wafer arechanged. In case the average polishing speed R_(p) is in the level 1range, no replacement of polishing pad nor change of polishingconditions of the product wafer is practiced.

In Step S12, in case the change of the polishing conditions is judged tobe necessary, the polishing condition setting unit 47 changes thepolishing conditions for the product wafer to proper conditions (StepS13).

In Step S13 for change of the product wafer polishing conditions, forexample, the polishing time is changed. In this case, using theconversion function f [Equation (11)] between the previously obtainedaverage polishing speed of the monitor wafer film and the averagepolishing speed of the product wafer, an average polishing speed R_(p) 'of product wafer is obtained from the average polishing speed R_(p) ofthe monitor wafer. `k` in Equation (11) is a proportional constant, tobe determined by the difference between the kind of the film which isthe object to be polished in the product wafer and the kind of the filmin the monitor wafer, and by the convex and concave shape of the productwafer. Furthermore, a predetermined target polishing amount X_(aim) isdivided by the average polishing speed R_(p) ' of the product wafer toobtain a proper polishing time t_(p) [Equation (12)]. And, the polishingtime of the product wafer may be set to the proper polishing time t_(p).

Equations (11) & (12)

And, after change of the polishing conditions, the process is returnedto Step S3, the changed polishing conditions are stored in the apparatuscontrol unit 48, and the polishing processing of the product wafer (StepS4) is re-started.

In Step S12, when the change of the polishing conditions of the productwafer is judged to be unnecessary, without changing the polishingconditions of the product wafer, the polishing processing of productwafer (Step S4) is re-started.

With the polishing method and CMP device as described above, thepolishing amount is measured by using a monitor wafer different from theproduct wafer, the monitor wafer having a film of uniform thickness onthe surface, so that it is possible to measure the polishing amountaccurately and evaluate the polishing situation accurately. Accordingly,the change with time of the polishing situation such as polishing speedattributed to the degradation of the polishing pad, polishing slurry,and the like can be met by the change of polishing conditions, or byreplacement of the polishing pad, whereby the polishing amount anduniformity in the wafer plane of the polishing amount can be stabilized.

For the monitor wafer, there is used a silicon wafer on the surface ofwhich about 5 μm of oxidized film is formed. The thickness of the filmin the monitor wafer is desirably sufficiently thick, but inconsideration of the measurable range with the optical film thicknessgauge, an oxidized film of about 3-5 μm is formed in this embodiment.This film thickness is determined under restriction of the filmthickness gauge, and is not to be limited to this range.

In Embodiment 1, there is shown an example in which the judgment ofpolishing pad replacement and change of polishing conditions areperformed by the control calculator 8. Good effect is obtainable withthe constitution containing either one only.

Namely, for example, when the constitution allows to make judgment onchange of the polishing conditions and setting, it is possible tostabilize the polishing amount of product wafer, uniformity of polishingamount in plane of the wafer, and the like can be stabilized.

In case of the constitution being such as to allow judgment onreplacement of polishing pad, it is possible to judge pertinentlydegradation of the polishing pad and stabilize the polishing amount ofthe product wafer, uniformity in wafer plane of polishing amount, andthe like.

In Embodiment 1, as shown in the flow chart of FIG. 2, a polishingsituation judging step S9 is provided, so that it is possible to judgefirst if there is any deficiency in polishing situation or not, and incase of deficiency, the processing is temporarily stopped to remove thedeficiency. As a result, the polishing amount of the product wafer,uniformity in wafer plane of the polishing amount, and the like can bestabilized.

Embodiment 2

FIG. 6 is a block diagram showing a CMP device according to Embodiment2, which gives an example in which run-in polishing after the polishingpad replacement judgement of completion of the running-in polishing canbe automatically performed. This CMP device comprises, as similar toEmbodiment 1, a CMP device body 1 and a control calculator 8 to controlit. However, the constitution in the control calculator 8 and the kindof the processing mode are different from those of Embodiment 1.

The control calculator 8 comprises a polishing situation indexcalculating unit 42, a polishing start judging unit 50, a temporarystoppage indicating unit 51, a polishing condition initial setting unit52, an apparatus control unit 48, and a mode selection unit 49.

The polishing situation index calculating unit 42 comprises, as similarto that in Embodiment 1, a film thickness memory unit and an calculationunit, and operates the polishing situation index such as polishingamount on the basis of the film thickness prior to polishing and thefilm thickness after polishing.

The polishing start judging unit 50 judges whether the polishingsituation index is within the allowable range or not, and instructs tostart polishing of the product wafer. The temporary stoppage instructingunit 51 instructs temporary stoppage of the apparatus on the basis ofthe judgment of the polishing start judging unit 50.

The polishing condition initial setting unit 52 initially sets thepolishing conditions for the product wafer at starting polishing of theproduct wafer.

With respect to the mode that can be selected by the mode selection unit49, there is further set, in addition to the product wafer polishingprocessing mode, monitor wafer containing processing mode, monitor waferpolishing processing mode, and monitor wafer recovery processing modesimilar to those of Embodiment 1, a dummy wafer polishing processingmode.

The dummy wafer polishing processing mode is a mode to carry out run-inpolishing by a dummy wafer (e.g., a silicon wafer on which no film isformed). The dummy wafer is carried to the CMP unit 6 and washing unit 7from a dummy wafer cassette which is housed in the wafer supply unit 2,polished and washed, and then returned to the dummy wafer cassette onthe wafer supply unit 2.

The apparatus control unit 48 gives instruction such as processing mode,polishing conditions, and the like to the CMP device body 1 to operateit, in the same manner as in Embodiment 1.

FIG. 7 is a flow chart which shows processing procedure of a polishingmethod in Embodiment 2, wherein there is explained the trial operationincluding the run-in polishing at the time of the replacement of thepolishing pad.

(1) The polishing pad is replaced (Step S31).

(2) The thickness of the film of the monitor wafer is measured by thefilm thickness measuring unit 5 in advance (Step S32) and the polishingsituation index calculating unit 42 of the control calculator 8 storesit (monitor wafer containing processing mode).

(3) The dummy wafers of the predetermined number of batches are polishedand washed in the CMP unit 6 and washing unit 7 (Step S33, dummy waferpolishing processing mode), and the polishing slurry is sufficientlyadapted into the polishing pad. The batch number may be determined byexperience. In this embodiment, the polishing processing of 3 minutes abatch is carried out for 4 batches.

(4) The monitor wafer is polished under the predetermined polishingconditions in the CMP unit 6 and the washing unit 7, and washed (StepS34, monitor wafer polishing processing mode).

(5) The thickness of the film of the monitor wafer is measured with thefilm thickness measuring unit 5 using, for example, an optical filmthickness gauge (Step S35, monitor wafer polishing processing mode).

(6) From the results of measuring the film thickness the polishingsituation index calculating unit 42 calculates the polishing situationindices of the monitor wafer such as polishing amount, uniformity inwafer plane of polishing amount, polishing shape inclination value,average polishing speed, and so on. (Step S36).

(7) The polishing start judging unit 50 judges whether the calculatedpolishing situation index is within the permissible range or not (StepS37), and if it is within the range, it instructs the start of polishingof the product wafer (Step S39). This judgment may be performed in thesame manner as the polishing situation index judgment of FIG. 3. In casethe polishing situation index is not within the allowable range,processing of the CMP device body 1 is temporarily stopped (Step S40),and for example the worker is caused to confirm the condition of fixingthe polishing pad, and the like to finish the processing of the controlcalculator 8.

(8) In case the start of polishing is instructed, the polishingcondition initial setting unit 52 sets the polishing conditions of theproduct wafer such as the polishing time (Step S38). As the polishingtime, for example, a moderate polishing time t_(p) obtainable inEquation (11) may be used.

(9) The trial operation is terminated and polishing processing of theproduct wafer is started (product wafer polishing processing mode).

In the CMP device and polishing method as described above, the trialoperation process including the run-in polishing after replacement ofthe polishing pad can be carried out in good efficiency almost withoutintervention of man's hand.

Furthermore, as the film thickness is measured by using a monitor waferhaving flat surface which is different from the product wafer havingconvex and concave parts on the surface as in Embodiment 1, thepolishing situation including the polishing amount and polishing speedcan be accurately evaluated. Consequently, at the time of the start ofpolishing the object to be polished for product, the polishingconditions of the product wafer can be appropriately determined.

Embodiment 3

FIG. 8 is a block diagram showing a constitution of a CMP deviceaccording to Embodiment 3, having a constitution of combinationEmbodiment 1 and Embodiment 2. Also, using a schematic plan view showingthe concrete disposition of the CMP device body 1, the wafer flow in theprocessing mode represented by the monitor wafer polishing process isconcretely explained.

The CMP device of this embodiment comprises a CMP device body 1 and acontrol calculator 8 for controlling the same.

The CMP device body 1 comprises wafer supply units 2a, 2b, 2c, a monitorwafer containing unit 4, a film thickness measuring unit 5, a CMP part6, a washing unit 7, and a wafer carrying unit 11. Each unit of the CMPdevice body 1 is constituted to operate in cooperation according to theinstruction of the processing mode in the control calculator 8.

The control calculator 8 has a constitution in which it is possible tochange over between a judging part A for practicing the routine productwafer polishing of FIG. 1 and a judging part B for practicing the trialoperation after replacement of the polishing pad of FIG. 6. Accordingly,it is applicable to both the polishing process of the product wafer andthe trial operation after replacement of the polishing pad.

The judging part A comprises a polishing situation judging unit 43, atemporary stoppage instructing unit 44, a pad replacement judging unit45, a pad replacement instructing unit 46, and a polishing conditionsetting unit 47.

The judging part B comprises a polishing start judging unit 50, atemporary stoppage instructing unit 51, and a polishing conditioninitial setting unit 52.

The polishing situation index calculated by the polishing situationindex calculating unit 42 is given to the polishing situation judgingunit 43 of the judging part A and the polishing start judging unit 50 ofthe judging part B. The apparatus control unit 48 can receive thepolishing conditions set by the polishing condition setting unit 47 ofthe judging part A and the polishing conditions set by the polishingcondition initial setting unit 52 of the judging part B. The processingmode selected by the mode selection unit 49 is given to the apparatuscontrol unit 48 in the same manner as in Embodiments 1 and 2.

With respect to the processing mode which can be selected by the modeselection unit 49, there are set the product wafer polishing processingmode, monitor wafer containing processing mode, monitor wafer polishingprocessing mode, monitor wafer recovery processing mode, and dummy waferpolishing processing mode, and so on as described above.

FIG. 9 is a schematic plan view showing a concrete constitution of theCMP device body 1.

In front portion of the CMP device body 1, there are provided cassetteports (wafer supply unit) 2a, 2b for placing a product wafer cassettefor loading and containing product wafers or a monitor wafer cassettefor loading and containing monitor wafers, and a cassette port 2c forplacing a dummy wafer cassette for loading and containing dummy wafers,on one side and the other side, respectively. In front of the CMP devicebody 1 there is set a cassette carrying device 30, which automaticallycarries the wafer cassettes to place the predetermined wafer cassette toany cassette port.

At the back of the cassette ports 2a, 2b, there is arranged a carryingrobot 11a, and behind the cassette port 2c, there is disposed a carryingrobot 11b. Between the carrying robots 11a and 11b, there is provided awafer stage 15 for temporarily placing the wafer. In the rear of thecarrying robot 11a there is a wafer stage 13 for temporarily placing thewafer, and at the back thereof there is provided a carrying robot 11c.On the lateral side between the wafer stage 13 and the carrying robot11c there is a monitor wafer containing port (cassette) 4 which cancontain 25 wafers.

On the further lateral side of the monitor wafer containing port 4,there is provided a delivery waiting port (cassette) 29, and behind thedelivery waiting port 29 there is provided a carrying robot 11d.

Behind the monitor wafer containing port 4, there is provided the CMPpart 6, and a wafer table 21 having 5 wafer holder 26 is provided at themiddle part thereof. Above the wafer table 21 there is provided apolishing board having a polishing pad, which is made to be able topolish 5 wafers at the same time.

Between the carrying robot 11c and the wafer table 21 there are arrangeda load side carrying arm 23 and a wafer load lift 22. Also, between thecarrying robot 11d and the wafer table 21 there are installed an unloadside carrying arm 25 and a wafer load lift 24.

Behind the unload side carrying arm 25 a scrub washing arm 27 isprovided.

On the lateral side of the carrying robot 11d, delivery waiting port 29,and carrying robot 11b, there is externally provided the washing unit 7.The washing part 7 is furnished with a scrub washer and a spin dryer. Inthe scrub washer, while supplying demineralized water, a sponge made ofpolyvinyl alcohol (PVA) is brought into contact with the wafer, wherebythe wafer is washed. In the spin dryer, the wafer is dried by revolvingat high speed and blowing off the demineralized water on the wafer.

On the lateral side of the cassette port 2a and the carrying robot 11athere is externally provided the film thickness measuring unit 5. FIG.10 is a schematic side view showing the film thickness measuring unit 5.The film thickness measuring unit 5 is of an optical interference typewith vertical arrangement of a spectrometer 61, a lens-barrel 62, a halfmirror 67, and an objective lens in this order, and a light source 63 isprovided on the lateral side of the half mirror 67. A wafer holdingstage 66 of the film thickness measuring unit 5 comprises a horizontalsliding mechanism and rotary mechanism for fitting the measuring pointpositions, and a lift mechanism for focusing. Further, on the lateralside there are provided an orientation flat position fitting mechanism65 for fitting orientation flat position and a wafer centeringmechanism. By these mechanism, it is possible to measure an optionalpoint of the wafer.

The monitor wafer S is fitted position by the orientation flat positionfitting mechanism 65 and wafer centering mechanism, and by theindication of the control calculator 8 the predetermined measuringposition is scanned and the film thickness is measured. The measuredfilm thickness is sent to the calculator 8 for control and storedtherein.

Next, explanation is given on the wafer flow in each processing modes tobe practiced in such CMP device, i.e., on the wafer flow in monitorwafer containing processing mode, product wafer polishing processingmode, monitor wafer polishing processing mode, monitor wafer recoveryprocessing mode, and dummy wafer polishing processing mode.

FIG. 11 is a schematic plan view showing the wafer flow in the monitorwafer containing processing mode.

By the cassette carrying device 30, the wafer cassette 74 in which themonitor wafer is contained is carried and placed on the cassette stage2a. Next, by the carrying robot 11a one monitor wafer is taken out fromthe wafer cassette 74 and carried to the film thickness measuring unit5.

The monitor wafer undergoes film thickness measurement with the filmthickness measuring unit 5, and the result of the film thicknessmeasurement is stored in the control calculator 8. When the monitorwafer whose film thickness measurement is completed is placed on thewafer stage 13 by the carrying robot 11a, the carrying robot 11c carriesit to the monitor wafer containing port 4 from the wafer stage 13.

By repeating the above motions 25 times, there are placed 25 monitorwafers on the monitor wafer containing port 4. These motions may becarried out at the time of the maintenance such as replacement ofpolishing pad or the like.

FIG. 12 is a schematic plan view showing the wafer flow in the productwafer polishing processing mode.

The wafer cassettes 71, 72 containing the product wafers are carried bythe cassette carrying device 30 and placed on the cassette ports 2a, 2b.

The product wafer is taken out from the wafer cassettes 71, 72 by thecarrying robot 11a and placed on the wafer stage 13. FIG. 12 shows thecase of taking out a product wafer from the wafer cassette 71. Theproduct wafer placed on the wafer stage 13 is carried to the wafer loadlift 22 by the carrying robot 11c.

The product wafer is centered by the wafer load lift 22, carried to thewafer holder 26 on the wafer table 21 by the load side carrying arm 23,and held by the means such as vacuum adsorption.

Subsequently, the wafer table 21 is rotated by 1/5 turn, and in the samemanner, the next product wafer is carried and held by another waferholder 26. By repeating this motion five times, the wafers are heldrespectively in all wafer holder 26.

Then, the polishing board having polishing pad on the lower surfacethereof descends, and while the slurry is supplied, either one or bothof the polishing board and the wafer table 21 rotate to polishchemically and mechanically the surface of the product wafer.

After completion of polishing by the lapse of the predetermined time,the polishing board rises, and the scrub washing arm 27 rotates to washthe surface of the product wafer by scrubbing. And, after 1/5 rotationof the wafer table 21, the product wafer is taken out from the waferholder 26 by the unload side carrying arm 25, carried to the unload lift24, and further carried to the delivery waiting port 29 by the carryingrobot 11d.

Subsequently, the wafer table 21 is rotated by 1/5, and in the samemanner, the next product wafer held by another wafer holder 26 iscarried to the delivery waiting port 29. By repeating such motion fivetimes, the product wafers after polishing held by all wafer holders 26are fully carried to the delivery waiting port 29.

Simultaneously with the above, on the carrying in side, a process tohave the next product wafer hold by the wafer holder 26 is carried out.

The product wafers recovered by the delivery waiting port 29 issequentially carried to the washing unit 7 by the carrying robot lid,washed, and dried. Subsequently, the product wafer is placed on thewafer stage 15 by the carrying robot 11b, and returned to the originalwafer cassettes 71, 72 by the carrying robot 11a.

FIG. 13 is a schematic plan view showing the wafer flow in the monitorwafer polishing processing mode.

The monitor wafer contained in the monitor containing port 4 is takenout by the carrying robot 11c and placed on the wafer load lift 22.Thereafter, in the same manner as in the product wafer, the monitorwafer is passed through polishing and washing processes.

The monitor wafer washed in the washing unit 7 is placed on the waferstage 15 by the carrying robot 11b, and further carried to the filmthickness measuring unit 5 by the carrying robot 11a.

In the film thickness measuring unit 5, the film thickness of themonitor wafer after the polishing processing is measured, and the resultof the film thickness measurement are sent to the control calculator 8.

The monitor wafer which completed the film thickness measurement isplaced on the wafer stage 13 by the carrying robot 11a, and returned tothe monitor wafer containing port 4 by the carrying robot 11c.

FIG. 14 is a schematic plan view showing the wafer flow in the monitorwafer recovery processing mode. The monitor wafer stored in the monitorwafer containing port 4 is taken out by the carrying robot 11c, placedon the wafer stage 13, and further carried by the carrying robot 11a tothe empty wafer cassette 74 placed in the cassette port 2a.

By repeating such motion 25 times, 25 monitor wafers are recovered fromthe monitor wafer containing port 4 to the wafer cassette 74. Thismonitor wafer recovery motion may also be performed at the time of themaintenance such as the polishing pad replacement and the like, in thesame manner as in the monitor wafer containing motion.

FIG. 15 is a schematic plan view showing the wafer flow in the dummywafer polishing processing mode.

The flow of the dummy wafer is the same as the wafer flow at thepolishing processing of the product wafer shown in FIG, 12, except thatthe dummy wafer is taken out from the dummy wafer cassette 73 stored inthe cassette port 2c by the carrying robot 11b, and returned to thedummy wafer cassette 73 by the carrying robot 11b.

The dummy wafer cassette has a role, besides supplying a dummy wafer atthe dummy wafer polishing processing, of supplying the dummy wafer tocover deficiency, in polishing processing of the product wafer, in casethe product wafer is less than the predetermined number (for example, 5wafers) for 1 batch.

By each wafer flow as above, the monitor wafer containing processing,product wafer polishing processing, monitor wafer polishing processing,monitor wafer recovery processing, and dummy wafer polishing processingcan be practiced.

The polishing method in Embodiment 3 is equivalent to that in which thereplacement of the pad and trial operation step S11 shown in FIG. 2 arereplaced by all the steps S31-S40 shown in FIG. 7. That is to say, theroutine operation process which is a routine product wafer polishingprocess is carried out by the method as explained in Embodiment 1, andthe trial operation process after replacement of the polishing pad iscarried out by the method as explained in Embodiment 2. These routineoperation process and trial operation process are carried out bychanging over between the judgment part A for routine operation processand the judgment part B for trial operation process in the controlcalculator 8.

Thus in the CMP device of Embodiment 3, the routine operation processand the trial operation process can be continuously practiced.

As shown in FIG. 13, the constitution is such that, in the polishingprocessing mode of the monitor wafer, the monitor wafer which issubjected to polishing processing is returned to the monitor wafercontaining port 4. And, as the polishing situation index calculatingunit 42 of the control calculator 8 is furnished with a film thicknessmemory unit, it can memorize the film thickness after polishing of themonitor wafer. Then, subsequent to the calculation of the polishingsituation index, by replacing the film thickness of the monitor waferafter polishing as a film thickness before polishing and memorizing, itis possible to use the monitor wafer repeatedly and measure thepolishing amount. Namely, by making the film of the monitor wafersufficiently thick, repeated use of the monitor wafer is possible. As aresult, the monitor wafer can be used in good efficiency, and it ispossible to decrease the number of containing processing's of themonitor wafer and the number of recovery processing's to improve theoperating rate of the CMP device.

Furthermore, by providing in the control calculator 8 the means forjudging whether the remaining film thickness of the monitor wafer issufficient to the removing amount in the next polishing processing ornot and means for instructing the replacement of the monitor wafer whenjudged to be insufficient, control of the monitor wafer can befacilitated.

In the flow charts of FIGS. 2 and 7, the results of the polishingsituation index by the polishing processing of the monitor wafer aredirectly reflected on the polishing conditions of the product wafer andpolishing pad replacement, but they may be reflected on the polishingconditions of the product wafer and the replacement of the polishing padafter several batches.

Needless to say, the method and apparatus according to the presentinvention are applicable to various chemical and mechanical polishingsuch as flattening of blanket tungsten (W), flattening of copper (Cu)wiring in Damacin method, and the like in addition to the flattening ofthe inter-layer insulation film on the silicon wafer by the CMP method.

As described above, according to the present invention system, since thepolishing amount is obtained by using the object to be polished forpolishing amount monitor, the polishing situation can be accuratelygrasped. And, by carrying out the processing's such as to change thepolishing conditions, and replace the polishing pad, and the like, withmonitoring the polishing situation, polishing amount or uniformity inplane of polishing amount or the like can be stabilized. As a result,formation of defective product can be suppressed, and product yield canbe improved.

Moreover, by automatically carrying out the trial operationautomatically judging the completion of the trial operation afterreplacement of the polishing pad, intervention of man's work can besuppressed, and the work can be efficiently carried out. Theconstitution may be such as to make automatic setting of the polishingconditions after replacement of the polishing pad.

As this invention may be embodied in several forms without departingfrom the spirit of essential characteristics thereof, the presentembodiments are therefore illustrative and not restrictive, since thescope of the invention is defined by the appended claims rather than bythe description preceding them, and all changes that fall within metesand bounds of the claims, or equivalence of such metes and boundsthereof are therefore intended to be embraced by the claims. ##EQU1##

What is claimed is:
 1. A chemical mechanical polishing apparatuscomprising: a port for an object to be polished;a polishing device forthe object to be polished using a polishing pad; a washing device forwashing the polished object: a measuring device for measuring thicknessof a film of a monitoring piece before and after polishing; acalculating unit for calculating a polishing amount on the basis of theresult of measurement of the thickness; means for judging whether thepolishing situation is normal or not on the basis of said polishingamount; means for one of setting and changing a polishing condition insaid polishing device on the basis of said polishing amount; and meansfor judging the completion of the run-in polishing after replacement ofthe polishing pad on the basis of said polishing amount.
 2. A chemicalmechanical polishing apparatus according to claim 1, further comprisingmeans for judging whether there is necessity or not for replacing thepolishing pad on the basis of said polishing amount.
 3. A chemicalmechanical polishing apparatus comprising:a port for an object to bepolished; a polishing device for the object to be polished using apolishing pad; a washing device for washing the polished object; ameasuring device for measuring thickness of a film of a monitoring piecebefore and after polishing; a calculating unit for calculating apolishing amount on the basis of the result of measurement of thethickness; means for judging whether the polishing situation is normalor not on the basis of said polishing amount; means for one of settingand changing a polishing condition in said polishing device on the basisof said polishing amount; a container for containing said monitoringpiece; a carrying device for carrying said monitoring piece to saidpolishing device from said container; a carrying device for carryingsaid monitoring piece to said washing device from said polishing device;a carrying device for carrying said monitoring piece to said measuringdevice from said washing device; and a carrying device for carrying saidmonitoring piece to said container from said measuring device.
 4. Achemical mechanical polishing apparatus according to claim 3, furthercomprisingmeans for judging whether there is necessity or not forreplacing the polishing pad on the basis of said polishing amount.
 5. Achemical mechanical polishing apparatus according to claim 4, furthercomprisingmeans for judging the completion of the run-in polishing afterreplacement of the polishing pad on the basis of said polishing amount.